Packaged aerosol compositions are well known for use in a variety of consumer product areas, including application of personal care products such as hairsprays, hairstyling or conditioning gels or mousses, cosmetics, antiperspirants and deodorants, aftershave or shaving gels and creams, first aid sprays, and so forth. Other consumer product areas include household, industrial, or agricultural application.
All such aerosol products typically contain an active ingredient, a liquid carrier for the active ingredient, and a suitable propellant. The propellant is in the form of a compressed gas, typically a liquefiable gas, which acts to expel the liquid carrier and active ingredient from the aerosol package to the site of application. Examples of aerosol propellants include halogenated hydrocarbons such as fluorohydrocarbons and chlorofluorohydrocarbons, hydrocarbon gases such as butane and propane and dimethyl ethane, carbon dioxide, and nitrous oxide, and many others.
The use of many of these propellants, however, has been restricted for environmental or other safety concerns. The use of chlorofluorocarbons, for example, has been limited due to concerns that it contributes to depletion of the ozone layer of the upper atmosphere. By contrast, hydrocarbon propellants are not believed to be associated with ozone layer depletion and are now used extensively in aerosolized consumer products. Even the use of these hydrocarbon propellants, as well as other volatile organic compounds (VOC), are now being limited due to safety concerns associated with the release of large amounts of VOC's into the atmosphere from aerosolized consumer products.
Recently, fluorinated hydrocarbon propellants such as 1,1-difluoroethane have been used as a replacement for the more commonly used hydrocarbon propellants. It is believed that these fluorinated hydrocarbons are less harmful to the environment than most hydrocarbon propellants, and that the use of these fluorinated hydrocarbons allows for the formulation of aerosol products with reduced VOC content. These fluorinated hydrocarbons are especially useful in anhydrous antiperspirant and hairspray compositions. It has been found, however, that the use of these fluorinated hydrocarbon propellants can result in corrosion of the metal liner or surface within the aerosol container containing the propellant even when the composition is an anhydrous system that would not otherwise promote such corrosion. It has been found that corrosion of the metal container results in the visible appearance of rust on the inner surface of the container, which was very surprising given that the rust was first identified in a completely anhydrous system, and also given that comparable compositions containing hydrocarbon propellants do not have the same rust or corrosion problem.
It has also been discovered that this surprising rust or corrosion problem occurs in anhydrous systems when the fluorinated hydrocarbon is used in the presence of a strong Lewis acid having a pKa of less than about 5.0 and a source of hydrogen bonded water (i.e. bound water). For antiperspirant compositions, the aluminum and/or zirconium polymer salt acts as a strong Lewis acid that also contains hydrogen bonded water. It has been found, quiet surprisingly, that when fluorinated hydrocarbon propellants are used in such antiperspirant compositions that some rust formation can be noted on the inner surface of many of the metal aerosol packages containing such compositions.
It has now been discovered that this surprising rust formation problem in anhydrous aerosol compositions as described herein can be corrected by any known or otherwise effective rust inhibition means suitable for use in aerosol containers and suitable for use in consumer products.
In view of the foregoing, it is therefore an object of the present invention to provide an aerosol package composition containing fluorinated hydrocarbons which do not provide for canister corrosion or rust formation. It is yet another object of the present invention to provide an anhydrous aerosol package composition which contains a fluorinated hydrocarbon, a Lewis acid, and a source of hydrogen bonded water, wherein the components of the composition do not react and cause canister corrosion or rust formation. It is yet another object of the present invention to provide an anhydrous aerosol antiperspirant package composition which contains fluorinated hydrocarbons and an aluminum and/or zirconium polymer salt, that do not react and result in the corrosion of a metal aerosol container. It is yet another object of the present invention to provide an anhydrous aerosol package composition wherein the inner surface of the aerosol container has been treated with a rust inhibitive material.